Field of the Disclosure
The invention relates to single or polyphase electric motors with a cage type rotor. Particularly this invention relates to these induction motors to operate at a higher power factor, for which therein is a reduction in the vector sum of the reactive power (kilovolt-amperes reactive/kvar). That is the angle of degrees between the real power (kilowatts/kw) and apparent power (kilovolt-amperes/kva) vectors without any sacrifice to the operational output of the motor, e.g. horsepower, torque, rpm, in any and all ranges of operational loading, from idle to full load.
Discussion of the Background
With the present rising cost of utilities, specifically electric power cost. The rising costs are in the form of higher charges per kwh (kilowatt hour), penalties for low pf (power factor) usually below 0.85 pf (if the plant demand is high enough for the utility company to apply the power factor reading for billing, if not then a charge of straight kva is used), and fuel surcharges. With induction motors extensive use and their high consumption of energy, government set standards have been imposed. EPCA of 1975. EPACT 1992. Furthermore the Energy Conservation Program: Energy Conservation Standards for Commercial and Industrial Electric Motors (amended EPCA of 1975) effective Jul. 28, 2014, with compliance starting Jun. 1, 2016. And expired EPACT incentives, the need for energy conservation is apparent.
With the electric motor being at the forefront for energy consumption, there is a specific point where electric motors are at their optimum point of efficiency as to their cost of operation, that is when they are being operated at their full rated horsepower load. Operation in a no load, under loaded or varying loaded state has a great effect on the cost of operation. When the electric motor that are running in a no load, under loaded or varying load, (the majority of induction motors are being operated in an under loaded state, approximately 50-70%) the cost of operation remains high. Because there is not a direct one to one relationship in the percentages between reduction of load to that of the operational characteristics of, or to operational costs of, an induction motor with the ever broadening angle between the real power (kw) and apparent power (kva) vectors, increasing kilovolts-amperes reactive (kvar), and decreasing the power factor (pf) energy waist becomes real apparent. Therefore, any improvement in the ratings of kw, kva, kvar and pf, results in a reduction in the cost of operation (energy used) of these ratings, pf and kvar are the characteristics (ratings) that are focused on for the best efficient use of power (energy), for reducing operational costs (energy consumption) in the induction motor. Maintaining the power factor at a high optimum level, or keeping it in a minimal spectrum of change at a high level in the induction motor, that reduces the kvar need, in any range of, or varying range of loading, including the full horsepower loading has always been and will always be a focus for energy concerns. So as the kvar increases, and pf decreases, a load with a low pf draws more current than a load with a higher pf for the same amount of useful power transferred. A high power factor is desirable since it minimizes the amount of reactive power (kvar) needed by the load, by reducing heat losses, maintaining voltage levels, and maximizing efficiency. With motors being operated in a no load to 50-70% loading, (the majority in the 50-70%) the power factor ratings for these motors, ranges from 0.17 to 0.73. Where on average, the rating at full load is 0.84 and the desired optimal rating for an induction motor is 0.95.
Several options had been presented, for example the use of dual winding motor designs such as in U.S. Pat. No. 7,034,426 and U.S. Pat. No. 7,227,288 granted to Gerald Goche. The 426 patent and 288 patent both disclose single and multiphase electric motors. Both with a main winding of a 2/3 ratio, to the 1/3 ratio of a de-saturation additional winding.
The 426 patent discloses a main winding and a de-saturation winding, wherein said de-saturation winding comprises a current flow in a different phase angle as to the main windings current flow phase angle. Furthermore 426 patent discloses having two conductors, with one conductor being one half the length of the other conductor.
The 288 patent discloses the de-saturation winding having a current flow opposite of the main winding current flow, that generates a field in the opposite direction of the main winding. Furthermore the 288 patent discloses the de-saturation winding having turns at 50-100% of predetermined turns of said main winding.
Furthermore 426 patent discloses a high efficiency, low current motor. On the other hand, 288 patent discloses a very high efficiency electric motor over a broad range of loads. As can be seen in 426 patent and 288 patent, Goche has failed to recognize what is the prime function of any electric motor winding, which is to produce magnetic fields, with specific magnetic flux densities, within varied specific core parts of the electric motor. The de-saturation of any part of the electric motors core has an undesired and unwanted effect, the loss of horsepower and torque, the prime driving force and load carrying function of any electric motor.
Another dual winding designs is disclosed in U.S. Pat. No. 4,187,457 and U.S. Pat. No. 4,446,416 granted to Cravens L. Wanlass. The 457 patent discloses a polyphase electric motor having controlled magnetic flux density, and the 416 patent discloses a polyphase electric machine having controlled flux density. Both patents describe a main winding with series capacitor, and a control winding wherein the stator core of each said patent switches between a non-saturated and a saturated condition.
The 457 patent further discloses a limiting effect of total energy transfer of the capacitor, wherein the end result is a motor that can be operated at maximum flux density, and wherein the capacitors limits energy to the rotor, so rotor current can be maximized. The motor winding inductance's can absorb only so much energy before the magnetic material of the stator saturates and discharges the capacitor. At the moment the motor material saturates, the capacitor discharges through the motor winding and the power source and charge up the capacitor in the opposite polarity.
The 416 patent further discloses that in a low load operation the flux density is low, and as load increases the flux density increases, furthermore that at low load, current flows in opposite directions across radically adjacent windings of the main winding and the control winding, and as load increases becomes increasingly in the same direction.
Wanlass also shows to disclose in 416 patent, a control winding that magnetically overlaps the magnetic poles of the main winding and center of the poles of control winding magnetically located substantially between the poles of the main winding and the control windings are in substantially physical radical alignment. Further discloses that by adding more capacitors you can increase starting torque, or if the control winding was disconnected, the motor would stall.
As can be seen in 457 patent and 416 patent, Wanlass has failed to recognize that the magnetic flux output of the winding is the driving force of the polyphase electric machine/motor, which is to produce horsepower and torque. Wanlass teaches in patent 416 that the current flow is across the two winding designs, then switches to the same direction across the two winding designs. Wanlass has not recognized the true nature of current flow in the polyphase electric machine of said patent 416, where the current flow of a circuit does not change unless the circuitry in itself changes, and that does not happen in said patent 416.
Wanlass in 416 patent, has also not recognized one of the characteristics of a capacitor, that is a capacitor is a resistive device to current flow. Where he explains that by adding capacitors to increase starting torque. With the adding of capacitors, to the already existing capacitor, you are increasing microfarads, therefore allowing more current flow, caused by the reduced resistance of the capacitors circuitry. With the increased current flow in the circuit, more flux is produced. Hence more starting torque. Wanlass explains that the motor would stall without the control winding of patent 416, and has not recognized the characteristics of inductive reactance and capacitive reactance and the result of their properties when combined in the same circuit. Further Wanlass in 457 patent has failed to recognize that the capacitors are constantly switching polarity, because of the use of alternating current. Wanlass details the capacitors charge in the opposite polarity after discharging.
Yet another winding designs are disclose in U.S. Pat. No. 4,808,868 and U.S. Pat. No. 4,959,573 granted to Gary D. Roberts. The 868 patent and 573 patent disclose an electromagnetic induction machine having regulated polar magnetic symmetry. The 868 patent claims a stationary stator circumferentially surround a rotor, and further claims wherein said rotor circumferentially surround said stationary stator of the same claimed machine. Roberts discloses to eliminate or control space harmonics in the air gap, negative sequence currents in the rotor and stator windings and increase efficiency.
The 868 patent discloses that the capacitor stored the unused energy returned to the stator winding and deliver stored energy to the magnetic circuit upon demand. The 573 patent discloses the capacitors deliver stored energy to compensate for additional power requirements.
Another winding designs are disclose in U.S. Pat. No. 6,331,760 granted to Oscar b. McLane Jr. McLane details a capacitive element connected in parallel with and tapped to each phase of a delta or wye connected stator winding, wherein the capacitive elements are alternately charged and discharged during operation, for storing energy from and releasing energy to the winding. Further McLane also discloses another method of reducing eddy current losses, to control flux density and uniformity thereof, in the region of the winding having multiple tap points and core de-saturation to optimize efficiency. Further detailing an improved controlled flux density motor which is comparable in size and weight. McLane details a structure and method that reduces the AC core losses and operates at reduced current under all conditions.
However, McLane has failed to see what the true meaning of motor efficiency is, as so many other inventors have done. They think that reducing the current is an increase in motor efficiency, with no regards for the standards that have been established and used to determine the efficiency rating of a motor. McLane has also failed to see the actual functionality of the capacitive elements and the type of circuitry that is associated with how they are being used in an alternating current circuit. It is also seen that his invention would not be advantageous, with its use of having to create a single or multiple tapped winding and having varying capacitive elements that would need to be constantly adjusted as the load of the motor changes. Use of a single or multiple tapped winding and determining said tap points would require engineering skills and abilities that someone who is skilled in the art of motor rewinding would not have. As for the controlled flux densities, McLane does not recognize, as so many others have also done, that the prime function of the stator winding is to produce magnetic fields, and those magnetic fields have to certain levels of flux densities in the various parts and multiple points in the stator core. That is to produce the horsepower and torque output, no matter what point of operational loading of motor. Furthermore a motor windings output is not determined by its size and weight. McLane's design is complex, of a single operational function, and requires skills far beyond that of someone familiar in the art.
Additionally is U.S. Pat. No. 6,788,031 granted to Larry Stuart Pendell. Pendell discloses an induction machine, more particularly refers to a broad class of electromagnetic machines where force or rotational torque or electrical energy are produced by the interaction of a driven and a generated magnetic field and currents which occurs because of induction. Pendell discloses a generator comprising a rotor which rotates at a speed determined by its design (number of poles, teeth and rotor coils) and capacitors connected to the energy windings or to auxiliary windings creating a self-excited induction generator. Further discloses that if the rotor of induction generator has some residual magnetism simply starting the engine and bringing it up to speed will start the process of establishing flux by induction in auxiliary windings. Pendell further detailing an induction generator, more so a self-excited induction generator, requires some energy source to produce excitation of the field windings. This excitation along with providing mechanical rotation of the conducting loops enables energy stored in the field of the rotor windings to be transferred to an output or energy winding. Further discloses as a motor, an energy source connected to the stator coils, creating a rotating stator field.
Still Pendell has failed to understand the induction generator, or more specifically the self-excited induction generator that uses a rotor, more specifically a cage type rotor that he discloses and the induction motor. This is clearly shown when he describes taking energy from a source (the grid), to produce energy, then send energy back to that source of energy (the grid). He discloses of a multiple winding motor as a generator, though it is actually operating as a motor, by the effect of the grid connection. Pendell further details in varying the speed of his generator as demand changes. In doing this the hertz of his generator would change, and if connected to the grid where the hertz remain constant, some type of catastrophic failure would occur, either in his generator or in the components between his generator and the grid. Pendell fails to realize that generators run at a constant speed, and that as demand changes there are other types of components that are used in conjunction with the generator specifically for demand change. Pendell also fails to see that it requires specific types of equipment and components, that are used to connect to the grid, so as to supply energy to the grid. Pendell's invention is not advantageous for use, do to complexity and probable high cost to manufacture, as to the simple self-excited design when used in conjunction with a grid tie invertor, and to constant speed mechanical drive source.
It is seen that McLane, Pendell, Roberts, Goche and Wanlass have all failed to recognize and to compare the overall characteristics of all their windings in their designs. Furthermore everyone cites that there invention is an improvement in the motors efficiency, without taking into consideration how motor efficiency is calculated. With this in mind, their efficiency ratings based on what they disclose would be over 100 percent. The mandated new requirements by the DOE for improved efficiency ratings for manufactured electric induction motors, of which now includes small motors of 3 horsepower and down, in single and three phase design. The efficiency of any motor has a peak limit of improvement. These new mandates and the costs associated with, the manufactures will pass on in a higher pricing for their motors. There are other types of equipment for power factor improvement (power factor correction), that require a monitoring and switching system so it can auto adjust, for if it did not and the power factor was over corrected, the equipment for which it was installed for could fail, and the associated cost for this power factor correction equipment can be extremely expensive.
Some of the direct costs for low power factor are a penalty for power factor below a predetermined value, or a credit for power factor above that predetermined value. Also charge for kvar hours, straight kva demand and a straight charge on the utility bill for the maximum value of kva used (included in this charge is a charge for kvar, since kvar increases the amount of kva). For it is the kva that the utility companies meter reads, along with the plant power factor (if applied and not a straight kva charge) to get the kwh reading. Other costs of low power factor are indirect, such as loss in efficiency in the equipment operation. There are certain harmonics (standing waves) that are produced by some types of equipment that has a negative effect on other equipment and its efficiency and cost of operation.
There are many in the industry that are oblivious to the effects of low power factor. The effects of low power factor are viewed only as a direct charge, when stated as such on their utility bill. Low power factor also adds a direct cost to the utility company, which is passed on. With everyone focusing on motor efficiency in its self, and not on actual use of the energy that is delivered to the motor and how it is used to operate the motor in all aspects that it can be used efficiently within the confines of an induction motors circuitry.